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Letters to the Editor |
and
Francesco Sardanelli, MD*
* Department of Radiology, University of Milan, Policlinico San Donato, Via Morandi 30, San Donato, Milan 20097, Italy. e-mail: tommasolupattelli@hotmail.com
Department of Radiology, Ferrarotto Hospital, Catania, Sicily, Italy
Editor:
Subintimal angioplasty is a relatively new technique that has been reported to successfully achieve recanalization of long occluded arterial segments in patients with critical limb ischemia. The growing interest in this intervention has led to a strict analysis of each technical and clinical aspect of the procedure, as well as its clinical outcome (1,2).
In the August 2004 issue of Radiology, Dr Spinosa and colleagues (3) reported their experience with percutaneous intentional extraluminal recanalization in patients who had chronic critical limb ischemia and who were poor candidates for infrainguinal arterial bypass surgery. In the article, the authors state that "by delaying subintimal tract dilation until distal reentry is accomplished, the risk of bleeding into adjacent extravascular tissues is limited, should perforation of the subintimal space occur." Moreover, they state that in this manner, "The potential for thrombus formation in the dilated subintimal space is also reduced," given that at their institute, "Anticoagulation with heparin is typically withheld until the guidewire has reentered the distal vessel lumen."
We would like to make a comment regarding the usefulness of balloon predilation and heparin administration before reentering the distal true lumen in subintimal angioplasty cases.
At our institute, we perform subintimal angioplasty according to the technique by Bolia et al (4). We usually enter the subintimal space by using a 0.035-inch J-tip guidewire that is then manipulated into a wide loop to be advanced distally. Once the lesion has been crossed and true lumen reentry is achieved, a balloon catheter of appropriate size is introduced, and the entire segment undergoes angioplasty. However, in some cases we find it very hard to advance the guidewire distally and/or to regain the true lumen. That is because the vessel may be calcified or a very tight stenosis or occlusion may be present somewhere in the artery. For this reason, when difficulty advancing or reentering is experienced we prefer to predilate the false lumen with an undersized balloon. With this maneuver, an easier advancement of the guidewire throughout the subintimal space is usually obtained. Moreover, when distal reentry may not be accomplished, balloon dilation of the desired site of reentry may at times result in a tear in the intima, which eventually leads to successful guidewire negotiation of the distal true lumen. Thus, although we always try to advance the guidewire in the subintimal space and reenter the true lumen without balloon predilation, this maneuver should be regarded as a valid option when dealing with very diseased vessels or when difficult reentry occurs.
Dr Spinosa and colleagues also state that limiting thrombus formation in the subintimal space (by delaying subintimal tract dilation until distal reentry is accomplished) is important because heparin is typically withheld until the guidewire has reentered the distal vessel lumen. To us, the use of heparin before guidewire distal reentry (we always administer an intravenous bolus of 5000 U heparin after introducer sheath insertion in the groin) is of extreme importance to prevent false lumen thrombosis at the time of and immediately after intentional vessel dissection. In fact, without early heparin administration, false channel thrombosis may occur, particularly when false lumen creation or distal reentry is not straightforward or is time consuming. Unfortunately, at the beginning of our experience, a whole-vessel thrombosis was seen immediately after false channel formation in a few patients in whom heparin had not been previously administered. Also, in all these patients, no resolution of thrombosis occurred after both repeat balloon dilation and heparin administration were performed. For this reason we strongly recommend the use of heparin before an attempt at subintimal angioplasty is made. Finally, should inadvertent artery perforation occur during guidewire advancement in the target vessel, the use of a tourniquet at the point of blood extravasation (along with prompt use of intravenously administered protamine) is likely to stop the vessel from bleeding in a short time.
References
Fairfax Radiology Consultants, Inova Fairfax Hospital, 2722 Merrilee Drive, Suite 240, Fairfax, VA 22031
e-mail: DJS4M@hsc.mail.mcc.virginia.edu
I thank Dr Lupattelli and colleagues for their interest in our article (1) and for their support of subintimal angioplasty. Careful review of the published literature regarding techniques as well as outcomes is an important step in the acceptance of any newly introduced treatment. Typically, such "new" procedures have been available for some time but are utilized by only a handful of physicians until their results reach a threshold of success that stimulates other physicians to utilize these "new" techniques. As other physicians perform these "new" procedures, "local" modifications are incorporated that streamline, economize, and optimize these "new" procedures and allow their successful and efficient use.
In Europe, thanks to the work of Bolia and many of his European colleagues (2), this threshold of success has long since been achieved, and many European physicians utilize subintimal angioplasty on a regular basis and incorporate important technical nuances, such as "balloon dilation of the desired site of reentry [that] may at times result in a tear of the intima, which eventually leads to successful guidewire negotiation of the distal true lumen" to achieve success, as described by Dr Lupattelli and colleagues in their letter to the editor. Sharing of these local "nuances" among physicians and staff at formal and informal meetings and in the literature ultimately leads to the evolution of a specific "new" technique that becomes standard among practicing clinicians until it is replaced by another "new" technique.
For example, predilation of the false lumen with an undersized balloon angioplasty catheter can undoubtedly be a useful technique and I have employed it in my experience before experimenting with different catheters and guidewires to try to streamline the formation of the subintimal channel. The use of hydrophilic guidewires and reinforced hydrophilic catheters to create the subintimal channel frequently makes predilation with balloon catheters unnecessary. The potential for significant thrombus formation is greatly limited, since the subintimal channel is "occluded" by the catheter, and no inflow is established because the entry to the subintimal channel is also occluded. This approach also limits the need for heparin since there is minimal, if any, blood to clot in the subintimal channel.
However, if the catheter fails to advance past any point in the subintimal channel, balloon dilation at the point of obstruction is necessary to allow advancing the catheter and guidewire to the level of reentry into the true lumen. Once balloon dilation of the subintimal channel is performed, particularly if this dilated channel communicates with the inflow vessel, then anticoagulation with heparin is necessary to prevent thrombus formation in the now enlarged subintimal channel.
Although heparin can be reversed and/or compression to the bleeding site can be performed if a perforation into the extravascular space occurs during subintimal channel creation, bleeding and pressure in an ischemic leg typically cause patient (and physician) pain resulting in potentially less patient cooperation, less time to complete the subintimal angioplasty, and a lower threshold for most physicians to quit. I believe that reserving balloon angioplasty of the subintimal tract along with heparin use for more difficult cases can potentially limit "failed" procedures when performing subintimal angioplasty.
Subintimal angioplasty provides an important addition to therapies available for the treatment of limb salvage in patients with chronic critical limb ischemia and offers a unique opportunity for interventional radiologists to increase their success with lower limb arterial revascularization, especially in patients with limited revascularization options. That is, however, until innovations with the technique are made that simplify it so that even surgeons and cardiologists are comfortable performing subintimal angioplasty.
References
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